The present invention relates to an ultrasonic transmission/reception method, ultrasonic transmission/reception apparatus, ultrasonic imaging method and ultrasonic imaging apparatus, and particularly to an ultrasonic transmission/reception method, ultrasonic transmission/reception apparatus, ultrasonic imaging method and ultrasonic imaging apparatus for imaging an object into which an ultrasonic contrast agent is injected.
In ultrasonic imaging, an echo of ultrasound transmitted into an object is used to capture a tomographic image, and the image is displayed as a B-mode image. Moreover, a Doppler shift of the ultrasonic echo is used to capture a dynamic image of blood flow etc., and the image is displayed as a color Doppler image.
When the signal intensity of the echo needs to be increased, a region of interest (ROI) is infused with a contrast agent using the blood flow. The contrast agent is a collection of microscopic bubbles having a diameter of several micrometers.
Such a contrast agent is broken up and disappears when exposed to ultrasound having a sound pressure greater than a certain level and will generate no echo next time. Therefore, the next imaging is performed after the contrast agent has again reached the site being imaged.
For this reason, the ultrasonic imaging using the contrast agent performs intermittent image capture (scanning) with a pause period of, for example, from several seconds to several tens of seconds after every imaging. Each tomographic image obtained from the scanning is displayed as a freeze image and is updated every time the next scanning image is obtained.
In order to make it possible to observe the state of the imaged site in real time during the pause period, the same region is imaged using ultrasound having a sound pressure reduced to a degree such that it does not break the contrast agent.
However, the image captured using the ultrasound having a sound pressure reduced to a degree such that the it does not break the contrast agent has poor quality because of the low SNR (signal-to-noise ratio) of the echo received signal.